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HUBS192 EXAM > GI System > Flashcards

GI System Flashcards

1
Q

Main component involved in mechanical digestion?

A

Motility

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2
Q

Main component involved in chemical digestion?

A

Secretion of fluid and enzymes

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3
Q

How does the nervous system regulate/control digestion?

  • ENS
  • CNS
A

ENS: primary neural system controlling GI function
CNS: modulates activity of ENS

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4
Q

What does the parietal peritoneum line?

A

the abdominal + pelvic cavities (peritoneal cavity)

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5
Q

What does the visceral peritoneum cover?

A

The external surfaces of most abdominal organs

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6
Q

What is mesentery?

A

Double layer of peritoneal membrane connecting organ to body wall

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7
Q
  • Structure of the peritoneal membrane

- What does it secrete?

A
  • Simple squamous epithelium

- Secretes serous fluid

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8
Q

parietal and visceral peritoneum

A

Single layer of peritoneal membrane

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9
Q

Omentum

A

Double layer of peritoneal membrane connecting organ to organ

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10
Q

Momentum and mesentery store what?

A

Fat

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11
Q

Arterial supply to abdominal viscera:

  • Which arteries branch off the abdominal aorta?
  • Where does this supply blood in a foetus?
A
  1. Celiac trunk (foregut)
  2. Superior mesenteric (midgut)
  3. Inferior mesenteric (hindgut)
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12
Q

Arterial supply to abdominal viscera:

  • Branches of the celiac trunk and which organs they supply
A
  1. Common hepatic
    - Liver
    - Duodenum
    - Pyloric stomach
    - Pancreas
  2. Left gastric
    - Lower oesophagus
    - Stomach
    - Liver
  3. Splenic
    - Spleen
    - Pancreas
    - Stomach
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13
Q

Arterial supply to abdominal viscera:

  • Branches of the superior mesenteric and which organs they supply
A
  1. Intestinal arteries
    - lieum
    - jejunum
  2. Ileocolic artery
    - ileum
    - cecum
    - appendix
  3. Colic arteries
    - ascending colon
    - Transverse colon
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14
Q

Arterial supply to abdominal viscera:

  • Branches of the inferior mesenteric and which organs they supply
A
  1. Left colic artery
    - Descending colon
  2. Sigmoid arteries
    - sigmoid colon
  3. superior rectal artery
    - rectum
    - anal canal
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15
Q

Characteristic of blood drained via hepatic portal circulation

A

nutrient rich

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16
Q

Composition of GI tube wall: mucosa

- What does it contain

A
  1. Epithelium (mucous secreting)
  2. Basement membrane
  3. Lamina propria (LFCT)
    - Gland ducts
    - Nerve fibres
    - BVs and lymph vessels
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17
Q

Composition of GI tube wall: submucosa

- What does it contain?

A
  • FCT
  • blood + lymph vessels
  • glands
  • meissner’s/submucosal plexus
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18
Q

Composition of GI tube wall: muscularis

A

Smooth muscle:

  • inner circular
  • outer longitudinal
  • myenteric plexus (b/w layers)
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19
Q

Composition of GI tube wall: adventitia

A

FCT

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20
Q

Which parts of the GI tract are lined w/ stratified squamous epithelium?
- purpose?

A

Mouth
Oesophagus
Anal canal
- protection

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21
Q

What epithelial tissue lines the SI

A

Simple columnar

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22
Q

What is the muscle transition in the oesophagus

A

skeletal to smooth

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23
Q

What epithelial tissue lines the stomach?

- Which cells line the gastric glands? What do they secrete?

A
  • Simple columnar
    Gastric glands:
  • Mucous cell; secretes mucous
  • Chief cell; secretes pepsinogen
  • Parietal cell; secretes HCl + intrinsic factor
  • Endocrine cell; secretes hormones (gastrin and ghrelin)
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24
Q

Epithelial tissue lining the LI?

A

Simple columnar

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25
Composition of the smooth muscle in the intestines?
- inner circular | - outer longitudinal
26
Which type of digestion occurs in the mouth?
Mechanical
27
Parotid salivary glands: - Secrete? - Relative size? - Located? - Secrete what % of total saliva
- Serous fluid only - Largest salivary glands - Inferior and anterior to the ear - 25-30% of total saliva
28
Submandibular salivary glands - Secrete? - Location of submandibular duct - Secrete what % of total saliva
- Secrete mixed serous and mucous - submandibular duct opens through papilla in the floor of the mouth - 60-70% of total saliva
29
Sublingual salivary glands - Secrete? - Located? - Secrete what % of total saliva
- Mucous - Multiply, tiny ducts open onto the anterior surface of the oral cavity - 3-5% of total saliva
30
Functions of saliva
- Moistens ingested material --> bolus - Moistens, cleanses and lubricates oral cavity - Begins chemical digestion of carbohydrates (amylase) - Antibacterial action (lysosomes) - Dissolves food --> taste
31
Epithelium of the oropharynx | - purpose
Stratified squamous | - protection
32
Oesophagus: - layers? - composition of layers? - What is b/w the oesophagus and the stomach? Made up of?
Layers 1. Mucosa - stratified squamous epithelium 2. Submucosa - mucous glands 3. Muscularis - Skeletal to smooth muscle 4. Adventitia Lower oesophageal sphincter - ring of thickened smooth muscle
33
Stomach: - 3 sections? - epithelium - muscularis layers (inner to outer) - Folds: name, made up of, allows for? - Sphincter?
- Fundus, body, pylorus - Simple columnar - oblique, circular, longitudinal - rugae; mucosa and submucosa; expansion - Pyloric sphincter
34
Characteristics of chief cells
- Rough ER | - Granules
35
Characteristics of parietal cells
- Lots of mitochondria - Large SA - Highly folded (microvilli)
36
Function of gastrin
- stimulates digestive function | - acts on PC to stimulate HCl secretion
37
Function of ghrelin
- Stimulates appetite
38
3 functions of omenta
1. Fat deposition 2. Immune contribution 3. Infection and wound isolation
39
What does the greater momentum attach?
Stomach to the transverse colon
40
Location and function of pyloric sphincter
- B/w stomach + SI | - Controls the release of chyme into the duodenum
41
What + where are the specialised cells in the duodenum + their purpose - Other function?
1. Mucous secreting cells in the epithelium: protection from acid 2. Alkaline mucous secreting glands in submucosa: protection from acid 3. Neutralise pH by stimulating secretion of bicarbonate
42
What are the layers of the SI wall + any structures w/in them
1. Mucosa: vili w/ microvilli 2. Submucosa: plicae circulares 3. Muscularis: inner circular and outer longitudinal 4. Adventitia
43
What is glycocalyx?
A glycoprotein coat on the microvilli which holds brush border enzymes for contact digestion.
44
What is segmentation?
Localised contractions of circular muscle; moves contents back + forth ---> mixes food w/ digestive juices + facilitates absorption
45
What does the submucosal plexus regulate?
Secretion
46
What does the myenteric plexus regulate?
Motility
47
Function of bile salts
Emulsify lipids
48
What does the pancreas produce?
Digestive enzymes + bicarbonate
49
What is the sphincter associated with the hepatopancreatic duct?
Sphincter of Oddi
50
What is the duct formed by the union of the pancreatic duct + the common bile duct? Leads into?
Hepatopancreatic duct | - duodenum
51
What anchors the transverse colon to the body wall?
Transverse mesocolon
52
Sections of the LI
Cecum --> ascending colon --> hepatic flexure --> transverse flexure --> splenic flexure --> descending colon --> sigmoid colon --> rectum --> anal canal
53
What is the sphincter/valve between the ileum and the sphincter?
ileo-caecal valve
54
What folds are associated w/ the LI?
Semilunar folds
55
What are haustra?
Sacs formed in the LI when taeniae coli are contracted
56
What are taeniae coli?
The outer longitudinal muscle layer of the LI arranged into tape-like strips
57
What are epiploicae appendices?
Small pouches of the peritoneum filled with fat and situated along the colon
58
Layers of the LI
1. Mucosa; contains deep mucosal invaginations (crypts) and goblet cells 2. Submucosa 3. Muscularis 4. Adventitia
59
State of sphincter muscles during the 3 stages of defecation
1. Rectum minimal stretch/pressure: internal contracted, external relaxed 2. Rectum stretched: internal relaxed, external contracted 3. Conscious defecation: both relaxed
60
What does the liver portal triad consist of? What do they transport?
1. Hepatic artery: oxygenated blood in from aorta 2. Hepatic portal vein: deoxygenated, nutrient-rich blood in from digestive organs 3. Bile duct: bile out from liver to gallbladder
61
What is the basis of spontaneous activity in the GI tract
Basal Electrical Rhythm (BER): 1. Spontaneous variations in membrane potential 2. Produce action potentials (when threshold reached) 3. Contractions
62
What is the fasting motility pattern? - Time - activity - function
- Migrating Motor Complex (MMC) - 4-5 hours after a meal, repeated approx. every 2h - 3 periods: inactivity, intermittent activity, intense activity - Function: house keeping (clears it out)
63
What are the feeding motility patterns? - Where do they occur - Function
1. Storage - Stomach - Distension 2. Peristalsis - Oesophagus, stomach, SI, LI - Propulsion 3. Segmentation - SI, LI - Mixing + exposure to absorptive surfaces
64
How does storage occur in the stomach?
1. Receptive relaxation: - increase in vol. w/out increase in pressure - Initiated by swallowing 2. Relaxation of smooth muscle: - reduced thickness
65
How does peristalsis facilitate the delivery of food? | - Activity over duration?
- Peristaltic waves initiated on greater curvature - First hour: gentle activity; after 60-300 mins: more intense activity - Allows propulsion and retropulsion
66
How much saliva do we produce per day?
1.5L
67
Composition of saliva and their functions
1. Mucus - Lubrication 2. NaHCO3/NaCl - Dilution + optimum pH 3. Enzymes (Amylase, lipase) - digestion
68
Which component of the CNS regulates saliva?
- Autonomic NS
69
Vol. of gastric secretions per day? Mainly composed of?
2-3L
70
What is the main gastric secretion when fasting?
Mucus
71
Composition of gastric secretion when feeding? Functions?
- NaCl - Acid: denatures proteins, pH, activates pepsinogen, protection - Mucus: protection - Bicarbonate - Pepsinogen (pepsin): digestion of proteins - Intrinsic factor: absorption of vitamin B12 (in SI)
72
3 Phases of gastric secretion regulation - Function - Stimuli - Response
1. Cephalic - Preparation for food - Stimuli = thought + chewing - Causes increased parasympathetic NS activity 2. Gastric - Regulates secretion in stomach - Stimuli = distension + presence of AAs - Causes parasympathetic + ENS to stimulate PC + CC + gastrin production 3. Intestinal - Controls amount of acid delivered to SI - Stimuli = food in duodenum/distension - PNS + ENS; Stimulates release of GIP, CCK and secretin; reduce gastric secretions
73
Vol. of pancreatic secretion per day
1-1.5L
74
Components of pancreatic secretion | - Secreted by?
1. Enzymes (acinar cells) | 2. Bicarbonate (ducts)
75
Pancreatic secretion - enzymes - What are the types? - What do they target? - Secretion stimulated by?
``` → Lipolytic - Lipase, phospholipase - target lipids → Amylytic - amylase - targets carbohydrates → Proteolytic - trypsin, chymotrypsin, carboxypeptidase - targets proteins → Nucleolytic - ribonuclease - deoxyribonuclease Stimulated by: - Cholecystokinin (CCK) ```
76
Pancreatic secretion - alkaline/HCO3 rich fluid - Produced by? - Function? - Stimulated by?
- Duct cells produce isosmotic HCO3 rich solution - Neutralise chyme (acidic from stomach) - Creates optimum pH (for pancreatic & intestinal enzymes) - Stimulated by secretin
77
Pancreatic secretion - CCK - What is it produced by? - Stimuli - What does it stimulate?
- Produced by duodenal endocrine cells in response to digestive products in lumen (AAS, fats, carbohydrates) - Stimulates enzyme secretion (acinar cells)
78
Pancreatic secretion - Secretin - Where is it produced? - Stimulus - What does it stimulate?
- Produced by duodenal endocrine cells - in response to ↑ [H+] in lumen - Stimulates HCO3- secretion (duct cells)
79
How much bile is secreted per day?
0.5L
80
Composition of bile
``` → Bile salts + lecithin - Fat digestion & absorption → HCO3 rich fluid - Neutralizes acid chyme → Bile pigments - Excretion ```
81
Biliary secretion - Regulation - Where is bile produced and stored? - What stimulates release? - Where is bile delivered to? - What does bile contain? - What is its function?
- Constantly produced by the liver and stored in gallbladder - Release stimulated by CCK - Delivered to SI - Contains cholesterol, waste products, alkaline fluid, bile salts and lecithin - Assists with lipid digestion
82
Vol. of intestinal secretion per day
1.5L
83
Intestinal secretions: SI + LI
``` SI - Mucus - NaHCO3 LI - mucus ```
84
Carbohydrate digestion
Polysaccharide --> hydrolysis (salivary + pancreatic amylase) --> disaccharide --> hydrolysis (brush-border enzymes) --> monosaccharide
85
Stages of lipid digestion
1. Emulsification - Large droplets --> smaller droplets - Disperses them - Stomach + SI 2. Stabilisation - Stops droplets from settling again - Bile salts - SI 3. Hydrolysis - TAGs ---> monoglycerides + fatty acids - Lipase + colipase - Lumen of SI 4. Formation of micelles - Allows insoluble droplets to stay in water - Bile salts surround groups of ffas/monoglycerols
86
Lipid digestion
Large fat droplet --> small droplets (emulsification) --> hydrolysis (lipase) --> fatty acids + monoglycerides + glycerol
87
What are the factors affecting absorption?
- Motility - Available surface area - Transport - Removal of substances from the interstitial space
88
How does motility affect absorption?
- Need correct rate of propulsion for digestion & absorption (otherwise abnormal bowel movement, i.e constipation, etc) - Exposure to absorptive surfaces
89
How does SA affect absorption?
- Rate of absorption proportional to SA | - Anatomical adaptions (villi, microvilli) maximise SA
90
What are the 2 pathways for solute absorption?
Two pathways: → Paracellular pathway - Solutes move b/w the cells, do not cross the cell membrane - Relatively non-selective (can cross of small enough) - Passive (requires a gradient) - Only barrier is tight junctions b/w cells → Cellular pathway (selective) - Solutes cross 2 cell membranes - Insoluble substances need transport proteins
91
Purpose of large blood flow in interstitial space?
Removes substances from interstitial space to maintain gradient (HOMG)
92
Absorption of water - Process? - Gradient set up by?
→ Osmosis | - Gradient set up by absorption of salts & nutrients
93
Absorption of Sodium (Na+) - Passive - Active
→ Passive movement via paracellular pathway → Active transport via the cells (requires transporters): - Na+ transport alone - Na+ absorption coupled to glucose or AAs
94
Absorption of Carbohydrates - Passive - Active
→ Passive - Monosaccharides - Diffuse down gradients via paracellular pathway → Active - Cotransport w/ Na+ across apical membrane via SGLT-1 - Crosses basolateral membrane via GLUT2 - Monosaccharides
95
Absorption of Proteins - Passive - Active
``` → Passive - Products of digestion (AAs) - Diffuse down gradient via paracellular pathway → Active - Cotransport w/ NA+ - AAs coupled to Na+ - Similar process to glucose ```
96
Absorption of Fat
→ Products of digestion are lipid soluble - Can diffuse into cell - Delivered to brush border via micelles (fatty acids + monoglycerides) - In epithelial cell: Synthesised into triglycerides, packaged into chylomicrons which exit the cell via exocytosis + enter lacteals
97
Absorption of Bile salt - Proportion reabsorbed? - Where does it occur? - Where does active transport occur? - Where does passive absorption occur?
→ Majority is reabsorbed - Occurs in distal portions of SI to promote fat absorption - Active transport in terminal ileum - Passive absorption in jejunum
98
Absorption of Vitamins - Fat soluble - Water soluble
→ Fat soluble (ADEK): absorbed w/ fats → Water soluble - Na+ dependent absorption (eg Vitamin C) - Vitamin B12 (intrinsic factor)
99
``` Absorption of Vitamin B12 - What does it involve? Where is this secreted? - How does it allow absorption? - Active or passive absorption? ```
→ Involves intrinsic factor (secreted by stomach): binds to vitamin B12 → Receptors in ileum bind IF/B12 complex → Vitamin B12 actively absorbed
100
What regulates conditions in intestinal lumen?
- vol. | - composition
101
``` Local reflexes (ENS) - mediated by which receptors in GI mucosa? What do they detect/monitor? ```
1) Mechanoreceptors - Deistension 2) Chemoreceptors - Chemical composition of lumen 3) Osmoreceptors - Osmolarity
102
Neural regulation - CNS role & components - Type of regulation? - Subdivisions and what they normally do
→ Extrinsic bidirectional regulation (sensory → effector) → 2 subdivisions of ANS 1) Parasympathetic NS - In general stimulates motility & secretion 2) Sympathetic NS: - In general inhibits motility & secretion
103
Endocrine cells - Paracrine action - True endocrine action
→ Paracrine action - Substance acts on cells in immediate vicinity of release - Provides regional control in response to local conditions → True endocrine action - Hormones released into circulation to target distant cells
104
Gastrin: - Secreted by? - In response to? - Acts on? - Function?
- Gastric cells in stomach - Gastric motility + secretions - Acts on parietal cells, gastric muscle - Stimulates secretion + motility
105
GIP: - Secreted by? - In response to? - Acts on? - Function?
- Small intestine - Fats in the SI - Acts on G cells/gastric muscle - Inhibits gastric secretion + motility
106
Secretin: - Secreted by? - In response to? - Acts on? - Function?
- Duodenum - Food/acid moving into duodenum - Parietal cells + pancreatic duct cells - Stimulates bicarbonate secretion + inhibits effects of gastrin (H+ secretion from PCs)
107
CCK: - Secreted by? - In response to? - Acts on? - Function?
- SI - Products of digestion entering duodenum - Pancreatic duct cells - Stimulates enzyme secretion; inhibits gastric secretion + motility
108
Smooth muscle in the GI tract: - What is the basal electrical rhythm (BER)? - What does it cause?
- The resting membrane potential of the GI tract smooth muscle - Constant fluctuation of the membrane potential above and below the threshold potential

HUBS192 EXAM (7 decks)

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